The overall goal of this project is acquisition of new data on development of the otolith organs and on involvement of the membranous labyrinth in ear pathology. A combination of light and electron microscopic methods will be used to study maturation of the human saccule and utricle in both pre- and post-natal material. Emphasis will be placed on early fetal development of the otoconial membranes. Work with human material will be supported and extended by developmental studies in the mouse as experimental animal model. Pathology of the human membranous labyrinth will be studied as appropriate cases become available. In this phase of the project, we expect to concentrate on investigation of congenital defects involving the vestibular apparatus.